1. Field of the Invention
The present invention relates to a fluid compressor and, more particularly, to a fluid compressor for compressing a refrigerant gas in a refrigeration cycle, for example.
2. Description of the Related Art
Various conventional compressors such as a reciprocating compressor and a rotary compressor are known to those skilled in the art. In these conventional compressors, a structure of a drive unit such as a crankshaft for transmitting a rotational force to a compression section and a structure of the compression section are complex, and the number of components used in the compressor is large. In addition, in order to improve compression efficiency in a conventional compressor, a check valve must be arranged on its delivery side. However, a pressure difference between the inlet and outlet sides of the check valve is large, and a gas tends to leak from the check valve. Therefore, compression efficiency is degraded. In order to solve this problem, high dimensional precision of the constituting components and high assembly precision must be maintained, thus resulting in high cost.
A screw pump is disclosed in U.S. Pat. No. 2,401,189. In this pump, a columnar rotary member is fitted in a sleeve, and a spiral groove is formed on the surface of the rotary member. A spiral blade is slidably fitted in the spiral groove. Upon rotation of the rotary member, a fluid, sealed between the adjacent turns of the blade in the space between the outer surface of the rotary member and the inner surface of the sleeve, is transported from one end of the sleeve to the other.
The screw pump can transport the fluid but does not have a function for compressing the fluid. In order to seal the transported fluid, the outer surface of the blade must be always in contact with the inner surface of the sleeve. During rotation of the rotary member, however, the blade itself is deformed in the groove, and it cannot easily slide smoothly in the groove. For these reasons, it is difficult to keep the outer surface of the blade in slidable contact with the inner surface of the sleeve, and therefore it is difficult to satisfactorily seal the fluid. As a result, a compression operation cannot be performed by the structure of the screw pump.